define tachyon

In iOS development, it is often used to define macros, or to modify some data types with const, and often developers do not know how to use them correctly, resulting in the confusion of macros and const decorations in the project.Can you tell the difference between the following? Do you know when to use it?#define Hscoder @ "Hansha haha"NSString*hscoder = @"Hansha haha";extern NSString*hscoder;extern Const

typedefIf it is placed outside all functions, its scope is from the beginning of its definition until the end of the file;If placed within a function, the defined field is defined from the beginning of the definition until the end of the function;#define:Scopes are defined from the beginning of the definition to the end of the entire file, whether within a function or outside of all functions.Define within the same compilation unit, even in different namespaces, the scope of the action is the sa

The difference is as follows: Constants defined with #define MAX 255 are of no type , given an immediate number, and the compiler simply links the defined constant value to the name of the defined constant, define the defined macro variable to be replaced at the time of preprocessing. Copy replacement is used where the constant is applied in the program; with const float MAX = 255; The defined constants hav

of an interesting thing to do, but the way we often use to create objects in object-oriented objects is: Car car=new car (); Using the New keyword is already popular, so we use the above method to define total feeling awkward, and to create new attributes and functions every time we call them, it is not practical. Down we look at the form definition class of the constructor. 2. Constructors This approach looks a bit like a factory function. The s

whether the method has parameters or not, and whether it has a return value:? No parameter no return value method? Non-parametric return value method? No return value method with parameter? Return value method with a parameterUse of no parameter-return-value method in JavaIf the method does not contain a parameter, and there is no return value, we call it a method without parameters and no return value.The use of the method is in two steps:The first step is to

Building a site in Dreamweaver is the second key step in the development of a Web site. Here the establishment of the site, in fact, is in the Dreamweaver to define the site, planning site structure, deployment development environment. Define the site is to better use the "file" panel to manage the site files, but also to reduce the occurrence of some errors, such as path error, link error and so on. Many b

PS Define patterns and fill tools how to use? 1, open the file you want to define as a fill pattern, and select the Rectangle selection tool. 2. Draw the area on the pattern that you want to define as a fill pattern, and then proceed to the next step. 3, select a good, click on the menu bar "edit" to select the definition of this pattern.

A document title, what is the best way to define it? To answer this question, imagine that we want to define the title of the article on a page, and we usually have three ways to achieve this simple goal: method One: Does it make sense? Although . Heading { font-size:24px; Font-weight:bold; Color:blue; } OK, now all the headings are marked with heading class in bold font size and blue. That's great!

Define private variable for maxfontsize. public var _maxfontsize:number = 15; Define Public Getter Method, mark the property As usable for the source of data binding, and specify the name of the binding event. [Bindable ("maxfontsizechanged")] Public function Get Maxfontsize (): number { return _maxfontsize; } Define public setter method. Public function set Maxf

/*#ifndef _stdafx_h#define _stdafx_h#include #include #include #include #endif*/ (1) Content: Write two lines at the beginning of the header file (StdAfx.h): #ifndef _stdafx_h #define _STDAFX_H//is typically an uppercase file name ············ ············ Write a line at the end of the header file: #endif (2) Role: The main purpose is to prevent the duplication of the header file containing and compiling F

We should be familiar with the span tag, but it is very troublesome to use it, especially when we need to define the width and height for it, html pages often use the span tag, however, some friends may not use this label well. They seem to find it useful, but it is very troublesome to use it, especially when you need to define its width and height. A friend once asked:Why does the width and height of sp

To write a good C language, a beautiful macro definition is very important. Macro definitions can help us prevent errors, improve code portability and readability, and more.In the software development process, there are often common or common functions or code snippets that can be written as functions or encapsulated as macro definitions. So is the function good or the macro definition good? This requires us to make a reasonable choice between the two.Let's look at an example, compare two number

Avascript learn several ways to define objects in JSTransferred from: http://www.cnblogs.com/mengdd/p/3697255.htmlThere is no concept of class in JavaScript, only objects.　　There are several ways to define an object in javascript:1. Extending its properties and methods based on existing objects2. Factory mode3. How to construct a function4. Prototype ("prototype") mode5. Dynamic Prototyping ModeI. Extending

[Conversion] understanding # define sreg (* (volatile unsigned char *) 0x5f)This definition is always very strange. I don't know why. I have a little bit of experience today. Please submit more bricks to the prawns ~~~ Embedded system programming requires programmers to use C language to access a fixed memory address. Since it is an address, according to the syntax rules of the C language, the number of addresses should be pointer type. Therefore, aft

PHP constants: Difference between define and const A constant is the identifier (name) of a simple value ). As its name implies, this value cannot be changed during script execution (except for so-called magic constants, they are actually not constants ). Constants are case sensitive by default. Constant identifiers are always capitalized. You can use the define () function to

After you create a Microsoft SQL Server 2005 Analysis Services (SSAs) project, you can use the project by defining one or more data sources that the project will use. When defining a data source, it defines the connection string information to be used to connect to the data source. For more information, see . In the following tasksAdventureworksdwThe sample database is defined as the data source of the Analysis Services Tutorial Project. For the purpose of this tutorial, the database is loc

Static variables only exist in the function scope. That is to say, static variables only exist in the stack. Generally, variables in a function are released after the function ends, such as local variables, but static variables do not. That is to say, when you call this function again, the value of this variable will be retained. Simplest definition method The define () function defines a constant. Constants are similar to variables, except that: Afte

Title, the implementation of operator+= and operator+ is given below.1sales_data2Sales_data::operator+=(ConstSales_data RHS)3 {4Units_sold + =Rhs.units_sold;5Revenue + =rhs.revenue;6 return* This;7 }8 9 Sales_dataTen operator+(ConstSales_data AMP;LHS,ConstSales_data RHS) One { ASales_data sum = LHS; -sum + = RHS; - returnsum; the}The code above is called operator+ to define the operator+=.First operator+ has two parameters whose parameter type

viewcontroller.m//oc High Efficiency 52 for multiple use type constants, less # define preprocessing directives/*** 1. do not define constants with preprocessing. The defined constants do not contain type information, and the compiler simply performs a find-and-replace operation on this basis before compiling. Immediately someone redefined the constant value, and the compiler does not produce a warning mess

I define a function that accepts the String parameter, but transmits a null value during the call. php will report a fatalerror, but the actual situation will indeed result in a null parameter, I want to define a function that specifies the parameter type and can accept null. what should I do? {Code ...} execute... I define a function that accepts the String para